I've seen a lot of posts on this related subject. I believe the current availability of Wolff hammer springs is 9, 10, 11, 12 & 14 (factory std) pounds. I believe the factory trigger re-set spring is around 10 pounds with the replacement Wolff spring being 8 pounds. The springs are suppose to be the same for the SP101 and GP100 revolvers.
Most of what I've read is a 10 pound hammer spring is the minimum for reliable primer ignition with "most" common factory ammo. Never heard of a problem with the 12 pound springs. As far as changing the spring goes, getting it out of the gun is no problem. Removing the old one and replacing it with a new one without one or both flying across the room is another matter. For the "do it yourselfer", a home made wood jig with a vertically drilled hole for the strut and a horizontal slot for removing the pin is needed - along with another wood block with a strut securing hole for top end compression. DO NOT use a vice or other hard metal securing device. You could easily end up bending, breaking or abraiding the strut.
The trigger re-set springs on the Rugers should probably be left alone. The factory weighted spring is just adequate when shooting rapid fire. Try rapid dry firing an SP or GP and you'll see what I mean. The action will lock up until the trigger is fully re-set.
Bottom line as stated previously though, if this is a personal defence gun, approach messing with the springs with caution. A light and silky smooth trigger is great for target shooting. But for defensive purposes, reliability is paramount. And when the adrenalin is pumping, that factory trigger is going to feel pretty light anyway. A smooth and consistant feeling trigger (not necessarily light) is prefered. And this will happen with a lot of dry/live fire cycles with Rugers.